Abstract We propose to apply targeted mass spectrometric methods to the analysis of specific O-glycoforms of proteins in the progression of liver disease to hepatocellular carcinoma (HCC). We have identified novel sialylated O- glycoform of liver secreted proteins significantly increased at progressive stages of liver disease. We propose to determine structure of the glycoforms and to evaluate extent of their presence on liver secreted glycoproteins. We will study association of the O-glycoforms with progressing stages of liver pathology by their direct quantification at specific sites of protein attachment in serum of patients. The O-glycoforms will be analyzed in combination with other markers identified in previous studies. We combine current concepts of disease mechanisms and advanced technologies to design improved serologic assays expected to complement biopsy and other non-invasive procedures in the assessment of liver disease. Non-invasive monitoring of liver disease progression to HCC is expected to influence optimal selection of therapeutic approaches and improve disease outcomes.